BB cutouts - On 70's De Rosas with pressed lugs, you generally find either a heart cutout or slots. The IC lugged bikes I've seen, i.e. through the 80's, I believe have a relieved shell where the slots do not perforate the shell (cables routed under the shell.)
TT cable guides - circa 1975.
Sloping crowns - from the early 80's throughout the decade, coexisting with the flat version.
Long-point vs. short-point lugs - these overlap on bikes until maybe 1975, when the short-points then predominate. (Can't say longer points don't occasionally appear on later bikes, though.)
Cast lugs - from about 1979. The IC lugged bikes are easy to spot because the seatlug ears are "kicked up" - the top of the ears actually forms a shelf at the same level as the top of the seattube. On pressed lug bikes, the ears are positioned lower.
Originally Posted by
miamijim
From searching I know there was period when they didnt have TT cable giudes etc. Perhaps we could collectively get a rough date for the following:
1. BB cutouts
2. TT cable guides
3. Sloping fork crowns
4. Long point vs. short point lugs
5. Cast lugs versus ?? Forged? How do you visibly tell the difference?
Thanks,
Jim